534
FXUS63 KARX 200522
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1222 AM CDT Sun Sep 20 2026

.KEY MESSAGES...

- Decreasing potential for additional heavy rainfall through
  this morning, though isolated amounts up to 1 inch are
  possible (20-30%) across portions of northeast Iowa and
  southwest Wisconsin.

- Potential for showers returns Monday into Monday night (20-40%).

- Cooler and drier conditions are expected through much of the
  new week.

&&

.DISCUSSION...
Issued at 1218 AM CDT Sun Sep 20 2026

Today: Rainfall Potential Over Northeast Iowa and Southwest Wisconsin

The surface boundary that was situated across the Upper Mississippi
River Valley over the past day or so has shifted south of the region
and is currently draped across central Iowa into northern Illinois.
Through the early morning hours, an upper level shortwave lifts
northward out of Nebraska and over the surface boundary,
redeveloping showers and storms as it does so.

Earlier forecasts suggested that portions of northeast Iowa and
southwest Wisconsin could see a few inches in additional rainfall,
but the bulk of 19.18z model solutions have trended most of the
additional rainfall associated with this upper wave to our south
with only a few suggesting the surface boundary is able to nudge
northward. Certainly tend towards the southern solution however as
stronger moisture transport and deeper moisture exists to our south
along the aforementioned boundary. Can`t rule out some transient
showers and perhaps a storm given a few hundred J/kg of MUCAPE
depicted in some solutions bringing isolated and brief heavy rain
around 1" (20-30%) through Sunday morning, mainly for those along
and south of Highway 18 closer to the surface boundary, though
portions of southwest Wisconsin south of I-90 may also see these
amounts as weak 925hPa frontogenesis sits across this region. That
said, but additional flooding impacts should largely remain south of
our area. Outside of these showers/storms, much of the area should
be dry throughout the day with perhaps some scattering clouds
throughout the afternoon.

Monday: Potential for Showers Returns

Monday into Tuesday brings additional potential for rainfall as the
upper level closed low currently over the northern Rockies shifts
eastward into the Upper Midwest. Currently thinking areas along and
south of I-90 will be favored to see shower activity during this
period as the current trajectory of the upper low and the placement
of a surface boundary suggests the strongest QG forcing should
reside across these areas.

Rainfall amounts should be on the lower side compared to the last
day or so with the 20.01z NBM suggesting amounts are favored to be
under 1 inch with only a 10-20% chance to exceed this amount. That
said, some flooding potential does exist, mainly across southeast
Minnesota and northeast Iowa, if amounts exceed 1 inch given the
saturated soils, but should largely be mitigated by fairly marginal
parameters for heavy rainfall.

Tuesday - Friday: Cooler and Drier

Cooler and more fall-like temperatures are in store for the Upper
Mississippi River Valley through much of the new week as high
pressure and lower heights become situated over the Great Lakes by
Tuesday with highs in the 60s to low 70s and lows in the 40s. A
drier airmass also sinks southward into the Upper Midwest during
this period, limiting any additional rainfall potential as we head
into next weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1218 AM CDT Sun Sep 20 2026

MVFR to LIFR ceilings are still being observed across the area.
These conditions will continue through at least late morning
before the low clouds begin to break up and lift. A return to
VFR conditions is forecast by early afternoon at the terminals
and should remain that way through the remainder of this TAF
cycle. The wind will mainly remain out of the northeast to east
with the potential for gusts up to 20-25 kts, mainly for KRST.

&&

.HYDROLOGY...
Issued at 1218 AM CDT Sun Sep 20 2026

Several rivers south of I-90 continue rising into or remain in flood
stage, namely the Cedar, Turkey, Upper Iowa, and Root River basins.
Additional rainfall is possible through this morning, primarily for
those areas along and south of Highway 18 across northeast Iowa and
southwest Wisconsin where an around 1" of additional rainfall is
possible. Moderate flooding on the Turkey River at Garber may
briefly touch Major flood stage around sunrise this morning given
the potential for additional rainfall, though is expected to quickly
crest and fall back to Moderate flood stage by the afternoon.
Similarly, the Turkey River at Elkader and the Cedar River at Austin
are expected to briefly touch Moderate flood stage and this morning
before cresting and falling into Minor Flood stage and Action stage
this afternoon.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch until 7 AM CDT this morning for WIZ061.
MN...None.
IA...Flood Watch until 7 AM CDT this morning for IAZ029-030.

&&

$$

DISCUSSION...Falkinham
AVIATION...Muscha
HYDROLOGY...Falkinham